Previously most of the liquid tight conduit manufactured and sold was the metal type which had a coiled steel spiral inside and a plastic jacket on the outside which made it liquid tight. As the conduit contained the conductive steel spiral, it was necessary to maintain a ground and electrically bond the metal in the conduit by use of a connector that had at least a metal ferrule which would be connected to the outlet box, panel, motor, etc.,by a metal body.
One version of the metal connector used a steel ferrule which covered the outside of the conduit and screwed into the inside of the conduit. It then worked in conjunction with a fitting and a nut to complete the assembly. Most brands also included a sealing gasket inside to insure a water tight assembly.
Most of the present art connectors for plastic conduit have a ferrule as part of the connector body. Most of these have no threads on the ferrule and they depend on a nut and one other clamping part to secure the cable.
Another connector has threads on the ferrule. However, on this product the threads terminate before going inside of the fitting. This fitting also uses a nut and a sealing gasket.
Another screw on connector is similar to the existing technology for die cast connectors for flexible metal conduit except that it is a molded plastic for use with non-metallic liquid tight (NMLT) conduit. This connector also employs a sealing gasket for the conduit to butt up against. The disadvantage of this product is that it will not work well unless the conduit is cut perfectly straight. It also does not have the finished appearance of most liquid tight fittings where the outside cut edge of the conduit is covered.